Why do I cry scratch and hurt myself?

I used to love life and be happy but since my life has changed a little im not sure how, my feelings have changed too! I find myself crying allot randomly at strange times in my life and thinking how bad my life is and how disapointed i feel with myself, i think everyone else is better than me and i dont fit in and cry allot, and once or twicei hit myself and scrath myself but not often just when i get angry. my parents are getting strict with me all of a sudden and thats when my attitude changed! i dont know what to do please help so i know whats hapening to myself! P.S IM 11